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. Changes in engine technologies and after-treatmentdevices can profoundly alter the chemical composition of the emittedpollutants. To investigate these effects, we characterized the emittedparticles' chemical composition of three diesel and four gasoline Euro 5light-duty vehicles tested at a chassis dynamometer facility. The dominantemitted species was black carbon (BC) with emission factors (EFs) varyingfrom 0.2 to 7.1 mg km−1 for direct-injection gasoline (GDI) vehicles,from 0.02 to 0.14 mg km−1 for port fuel injection (PFI) vehicles, and0.003 to 0.9 mg km−1 for diesel vehicles. The organic matter (OM) EFs varied from 5 to 103 µg km−1 for GDI gasoline vehicles, from 1 to 8 µg km−1 for PFI vehicles, and between 0.15 and 65 µg km−1 for the diesel vehicles. The first minutes of cold-start cycles contributed the largest PM fraction including BC, OM, andpolycyclic aromatic hydrocarbons (PAHs). Using a high-resolution time-of-flight mass spectrometer (HR-ToF-AMS), we identified more than 40 PAHs in both diesel andgasoline exhaust particles including methylated, nitro, oxygenated, and aminoPAHs. Particle-bound PAHs were 4 times higher for GDI than for PFIvehicles. For two of the three diesel vehicles the PAH emissions were belowthe detection limit, but for one, which presented an after-treatment devicefailure, the average PAHs EF was 2.04 µg km−1, similar to theGDI vehicle's values. During the passive regeneration of the catalysed diesel particulate filter(CDPF) vehicle, we measured particles of diameter around 15 nm mainlycomposed of ammonium bisulfate. Transmission electron microscopy (TEM) images revealed the presence ofubiquitous metal inclusions in soot particles emitted by the diesel vehicleequipped with a fuel-borne-catalyst diesel particulate filter (FBC-DPF).X-ray photoelectron spectroscopy (XPS) analysis of the particles emitted by the PFI vehicle showed the presenceof metallic elements and a disordered soot surface with defects that couldhave consequences on both chemical reactivity and particle toxicity. Our findings show that different after-treatment technologies have animportant effect on the emitted particles' levels and their chemicalcomposition. In addition, this work highlights the importance of particlefilter devices' condition and performance.

atmospheric chemistry and physics

Technical note: Emission factors, chemical composition, and morphology of particles emitted from Euro 5 diesel and gasoline light-duty vehicles during transient cycles